用户的创建流程

一个用户，到底是怎么被创建出来的呢？

/etc/passwd    用户账户信息

/etc/shadow    安全用户账户信息

/etc/group 　　组账户信息

/etc/gshadow　　安全组账户信息

/etc/default/useradd   　账户创建时的默认值。(不指定参数时就会使用这个文件中的默认值)

[root@python ~]# cat /etc/default/useradd 
# useradd defaults file
GROUP=100    # 默认组
HOME=/home   # 默认家目录
INACTIVE=-1  # 是否启用过期
EXPIRE=      # 过期的时间
SHELL=/bin/bash  # 默认的shell
SKEL=/etc/skel   # 默认的home文件夹中默认的文件  从这里拷贝的
CREATE_MAIL_SPOOL=yes  # 要不要给用户创建邮箱

/etc/skel　　  包含默认文件的目录

[root@python skel]# ll -a
总用量 24
drwxr-xr-x.   3 root root   78 4月  11 2018 .
drwxr-xr-x. 149 root root 8192 7月   2 19:35 ..
-rw-r--r--.   1 root root   18 10月 31 2018 .bash_logout
-rw-r--r--.   1 root root  193 10月 31 2018 .bash_profile
-rw-r--r--.   1 root root  231 10月 31 2018 .bashrc
drwxr-xr-x.   4 root root   39 5月  16 05:24 .mozilla

/etc/login.defs  　　Shadow 密码套件配置。

[root@python ~]# cat /etc/login.defs  
#
# Please note that the parameters in this configuration file control the
# behavior of the tools from the shadow-utils component. None of these
# tools uses the PAM mechanism, and the utilities that use PAM (such as the
# passwd command) should therefore be configured elsewhere. Refer to
# /etc/pam.d/system-auth for more information.
#

# *REQUIRED*
#   Directory where mailboxes reside, _or_ name of file, relative to the
#   home directory.  If you _do_ define both, MAIL_DIR takes precedence.
#   QMAIL_DIR is for Qmail
#
#QMAIL_DIR    Maildir
MAIL_DIR    /var/spool/mail
#MAIL_FILE    .mail

# Password aging controls:
#
#    PASS_MAX_DAYS    Maximum number of days a password may be used.
#    PASS_MIN_DAYS    Minimum number of days allowed between password changes.
#    PASS_MIN_LEN    Minimum acceptable password length.
#    PASS_WARN_AGE    Number of days warning given before a password expires.
#
PASS_MAX_DAYS    99999
PASS_MIN_DAYS    0
PASS_MIN_LEN    5
PASS_WARN_AGE    7

#
# Min/max values for automatic uid selection in useradd
#
UID_MIN                  1000
UID_MAX                 60000
# System accounts
SYS_UID_MIN               201
SYS_UID_MAX               999

#
# Min/max values for automatic gid selection in groupadd
#
GID_MIN                  1000
GID_MAX                 60000
# System accounts
SYS_GID_MIN               201
SYS_GID_MAX               999

#
# If defined, this command is run when removing a user.
# It should remove any at/cron/print jobs etc. owned by
# the user to be removed (passed as the first argument).
#
#USERDEL_CMD    /usr/sbin/userdel_local

#
# If useradd should create home directories for users by default
# On RH systems, we do. This option is overridden with the -m flag on
# useradd command line.
#
CREATE_HOME    yes

# The permission mask is initialized to this value. If not specified, 
# the permission mask will be initialized to 022.
UMASK           077

# This enables userdel to remove user groups if no members exist.
#
USERGROUPS_ENAB yes

# Use SHA512 to encrypt password.
ENCRYPT_METHOD SHA512 

用户的创建就是，依靠这些文件进行创建的。

常用的东西。。。

作业：

创建三个用户 harry tom natasha

要求harry tom 附加到admin 组

natasha 不允许登录

修改默认创建用户环境：

要求用户家目录为 /home

uid， gid 从1000开始

登录shell 为 /bin/csh

要求：

使用 useradd  a

创建 a 的家目录为/rhome/a uid 100 gid 1000  shell:/bin/csh